Why percent yield sometimes less than 100% in chemistry experiments?

[harveycannon]

Homework Statement

I'm learning about percent yield in chemistry labs and noticed that the percent yield is often less than 100%.

What are the most common reasons for this?

Relevant Equations

Percent Yield = (Actual Yield ÷ Theoretical Yield) × 100

Also, when calculating percent yield, do we always use the same formula?

I understand that percent yield compares actual and theoretical yield, but I want to make sure I'm doing the calculation correctly.

 

[Mayhem]

Small thing. Percent yield = (actual yield / theoretical yield) * 100.

Without the 100 factor, you just get a ratio, not a % expression.

 

[harveycannon]

Sorry, I forgot to multiply 100 in the equation. It's corrected now.